其实Java Mail samples包含一个IMAP IDLE的例子，如下。
除此之外，IdleManager class 可能很有趣。
/*
* Copyright (c) 1996-2010 Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Oracle nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.util.*;
import java.io.*;
import javax.mail.*;
import javax.mail.event.*;
import javax.activation.*;
import com.sun.mail.imap.*;
/* Monitors given mailbox for new mail */
public class monitor {
public static void main(String argv[]) {
if (argv.length != 5) {
System.out.println(
"Usage: monitor <host> <user> <password> <mbox> <freq>");
System.exit(1);
}
System.out.println("\nTesting monitor\n");
try {
Properties props = System.getProperties();
// Get a Session object
Session session = Session.getInstance(props, null);
// session.setDebug(true);
// Get a Store object
Store store = session.getStore("imap");
// Connect
store.connect(argv[0], argv[1], argv[2]);
// Open a Folder
Folder folder = store.getFolder(argv[3]);
if (folder == null || !folder.exists()) {
System.out.println("Invalid folder");
System.exit(1);
}
folder.open(Folder.READ_WRITE);
// Add messageCountListener to listen for new messages
folder.addMessageCountListener(new MessageCountAdapter() {
public void messagesAdded(MessageCountEvent ev) {
Message[] msgs = ev.getMessages();
System.out.println("Got " + msgs.length + " new messages");
// Just dump out the new messages
for (int i = 0; i < msgs.length; i++) {
try {
System.out.println("-----");
System.out.println("Message " +
msgs[i].getMessageNumber() + ":");
msgs[i].writeTo(System.out);
} catch (IOException ioex) {
ioex.printStackTrace();
} catch (MessagingException mex) {
mex.printStackTrace();
}
}
}
});
// Check mail once in "freq" MILLIseconds
int freq = Integer.parseInt(argv[4]);
boolean supportsIdle = false;
try {
if (folder instanceof IMAPFolder) {
IMAPFolder f = (IMAPFolder)folder;
f.idle();
supportsIdle = true;
}
} catch (FolderClosedException fex) {
throw fex;
} catch (MessagingException mex) {
supportsIdle = false;
}
for (;;) {
if (supportsIdle && folder instanceof IMAPFolder) {
IMAPFolder f = (IMAPFolder)folder;
f.idle();
System.out.println("IDLE done");
} else {
Thread.sleep(freq); // sleep for freq milliseconds
// This is to force the IMAP server to send us
// EXISTS notifications.
folder.getMessageCount();
}
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}